1. Field of the Invention
This invention relates to a process for the production of alkylbenzenes and more particularly to a process which comprises alkylating an aromatic hydrocarbon containing a side-chain in which at least one hydrogen atom is bonded to a carbon atom alpha to the nucleus with an olefin in the presence of a novel catalyst.
2. Prior Art
It is known to produce alkylbenzenes by reacting a benzene with an alkylhalide or corresponding olefin in the presence of a Friedel-Crafts catalyst. This reaction however has often resulted in mixtures containing numerous isomers, which in turn required precise fractionation to give a selected product.
Another process is known for the production of alkylbenzenes in which aromatic hydrocarbons are reacted with olefins in the presence of an alkali metal such as lithium, sodium and potassium, as reported for example by H. Pines et al in the Journal of American Chemical Society, 78 4316 (1956).
British Pat. No. 1,269,280 discloses alkylating an aromatic hydrocarbon with a mono-olefin in the presence of a catalyst prepared by dispersing an alkyl metal on a potassium compound.
Such prior art processes using alkali metal catalysts involve less isomers than would be the case with Friedel-Crafts catalysts, but have a drawback in that aromatics reactivity is low and intended alkylbenzenes selectivity is also low due to large amounts of by-produced isomeric alkylbenzenes and olefinic dimers. The aforementioned catalysts are mostly prolonged in reaching maximum activity, requiring so much time to stabilize the reaction. Furthermore, they would often induce polymerization reactions with resultant polymers deposited on the catalyst surfaces to slowly deplete the catalytic activity. Concommitant with reduced catalytic activity, product selectivity tends to decline. Most deactivated catalysts would become solidified with resinous polymers within the reactor, but part of them remain still active which would cause explosion or fire on contact with oxygen or moisture in the atmosphere when removing the catalyst for replacement.
The prior art catalysts contain less than 5 weight percent, or usually only 1-3 weight percent of sodium or potassium that can be deposited on the carrier due to this carrier being inert and small in porosity rate. Attempts to deposit more than 5 weight percent of such alkali metals would result in muddy coagulates on the carrier surfaces, leading to loss of catalytic activity.